As is known, already commercially available treadmills are generally constituted by a belt that runs continuously around a free roller and a driving roller that is associated with motor means for imparting the selected travel speed to the belt.
Although these embodiments have proved to be valid in many respects, they have been found to be susceptible of improvements especially as regards constructive simplicity and as regards the possibility to tilt the belt gradually and steplessly during sports exercise without requiring the athlete to step off the treadmill or interrupt his pace.